Lubricating oil compositions comprising a molybdenum compound and a zinc dialkyldithiophosphate

ABSTRACT

Provided herein are lubricating oil compositions comprising a major amount of a base oil, at least one oil-soluble molybdenum compound and a zinc dialkyldithiophosphate compound, wherein the molybdenum content derived from the molybdenum compound is at least 10 ppm based on the total weight of the lubricating oil composition and the phosphorus content derived from the zinc dialkyldithiophosphate compound is about 200 to 500 ppm based on the total weight of the lubricating oil composition. The lubricating oil composition can further comprise at least one additive. Methods of making and using the lubricating oil compositions are also described.

FIELD

Provided herein are lubricating oil compositions comprising a base oil,an oil soluble molybdenum compound and a zinc dithiophosphate compound.Methods of making and using the lubricating oil compositions are alsodescribed.

BACKGROUND

Lubricating oil compositions used to lubricate internal combustionengines contain base oil of lubricating viscosity, or a mixture of suchoils, and additives used to improve the performance characteristics ofthe oil. For example, additives are used to improve detergency, toreduce engine wear, to provide stability against heat and oxidation, toreduce oil consumption, to inhibit corrosion, to act as a dispersant,and to reduce friction loss. Some additives provide multiple benefits,such as dispersant-viscosity modifiers. Other additives, while improvingone characteristic of the lubricating oil, have an adverse effect onother characteristics. Thus, to provide lubricating oil having optimaloverall performance, it is necessary to characterize and understand allthe effects of the various additives available, and carefully balancethe additive content of the lubricant.

It has been proposed in many patents and articles (for example, U.S.Pat. Nos. 4,164,473; 4,176,073; 4,176,074; 4,192,757; 4,248,720;4,201,683; 4,289,635; and 4,479,883) that oil-soluble molybdenumcompounds are useful as lubricant additives. In particular, the additionof molybdenum compounds to oil, particularly molybdenum dithiocarbamatecompounds, provides the oil with improved boundary frictioncharacteristics and bench tests demonstrate that the coefficient offriction of oil containing such molybdenum compounds is generally lowerthan that of oil containing organic friction modifiers. This reductionin coefficient of friction results in improved antiwear properties andmay contribute to enhanced fuel economy in gasoline or diesel firedengines, including both short- and long-term fuel economy properties(i.e., fuel economy retention properties). To provide antiwear effects,molybdenum compounds are generally added in amounts introducing fromabout 350 ppm up to 2,000 ppm of molybdenum into the oil. molybdenumcompounds are effective antiwear agents and may further provide fueleconomy benefits, such molybdenum compounds are expensive relative tomore conventional, metal-free (ashless) organic friction modifiers

Therefore, it is desirable to find a lubricating oil composition thatprovides improved fuel economy benefit; demonstrates excellent wearprotection characteristics, is relatively low in cost.

SUMMARY

Provided herein are lubricating oil compositions that provide animproved friction reduction. The lubricating oil compositions comprising

i) a major amount of a base oil,

ii) at least one oil-soluble molybdenum compound and

iii) a zinc dialkyldithiophosphate compound,

wherein the molybdenum content derived from the molybdenum compound isat least about 10 ppm based on the total weight of the lubricating oilcomposition and the phosphorus content derived from the zincdialkyldithiophosphate compound is about 200 to 500 ppm based on thetotal weight of the lubricating oil composition.

In certain aspects, the base oil is present in an amount greater thanabout 40%, 50%, 60% or about 70% by weight of the lubricating oilcompositions.

In certain embodiments, the lubricating oil composition disclosed hereinfurther comprises at least one additive selected from the groupconsisting of antioxidants, antiwear agents, detergents, rustinhibitors, demulsifiers, friction modifiers, multi-functionaladditives, viscosity index improvers, pour point depressants, foaminhibitors, metal deactivators, dispersants, corrosion inhibitors,lubricity improvers, thermal stability improvers, anti-haze additives,dyes, markers, and combinations thereof.

Also provided herein are methods of making lubricating oil compositions.In one aspect, the methods comprise the step of mixing

i) a major amount of a base oil,

ii) at least one oil-soluble molybdenum compound and

iii) a zinc dialkyldithiophosphate compound,

wherein the molybdenum content derived from the molybdenum compound isat least about 10 ppm based on the total weight of the lubricating oilcomposition and the phosphorus content derived from the zincdialkyldithiophosphate compound is about 200 to 500 ppm based on thetotal weight of the lubricating oil composition. In certain embodiments,the molybdenum compound and the zinc dialkyldithiophosphate compoundused as described herein show synergy and resulting low frictioncoefficient in prototype GF-5 lubricating compositions.

Also provided herein are methods of lubricating a motor engine with alubricating oil compositions provided herein. In one aspect, the methodscomprise the step of operating the engine with the lubricating oilcomposition of provided herein.

Other embodiments will be in part apparent and in part pointed outhereinafter.

DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a plot of friction by High Frequency Reciprocating Rigtest (HFRR) versus phosphorus content of the lubricant oil compositionsdescribed herein.

DEFINITIONS

To facilitate the understanding of the subject matter disclosed herein,a number of terms, abbreviations or other shorthand as used herein aredefined below. Any term, abbreviation or shorthand not defined isunderstood to have the ordinary meaning used by a skilled artisancontemporaneous with the submission of this application.

“A major amount” of a base oil refers to the amount of the base oil isat least 40 wt. % of the lubricating oil composition. In someembodiments, “a major amount” of a base oil refers to an amount of thebase oil more than 50 wt. %, more than 60 wt. %, more than 70 wt. %,more than 80 wt. %, or more than 90 wt. % of the lubricating oilcomposition.

“Sulfated ash content” refers to the amount of metal-containingadditives (e.g., calcium, magnesium, molybdenum, zinc, etc.) in alubricating oil and is typically measured according to ASTM D874, whichis incorporated herein by reference.

A composition that is “substantially free” of a compound refers to acomposition which contains less than 20 wt. %, less than 10 wt. %, lessthan 5 wt. %, less than 4 wt. %, less than 3 wt. %, less than 2 wt. %,less than 1 wt. %, less than 0.5 wt. %, less than 0.1 wt. %, or lessthan 0.01 wt. % of the compound, based on the total weight of thecomposition.

A composition that is “free” of a compound refers to a composition whichcontains from 0.001 wt. % to 0 wt. % of the compound, based on the totalweight of the composition.

In the following description, all numbers disclosed herein areapproximate values, regardless whether the word “about” or “approximate”is used in connection therewith. They may vary by 1 percent, 2 percent,5 percent, or, sometimes, 10 to 20 percent. Whenever a numerical rangewith a lower limit, R^(L), and an upper limit, R^(U), is disclosed, anynumber falling within the range is specifically disclosed. Inparticular, the following numbers within the range are specificallydisclosed: R=R^(L)+k*(R^(U)−R^(L)), wherein k is a variable ranging from1 percent to 100 percent with a 1 percent increment, i.e., k is 1percent, 2 percent, 3 percent, 4 percent, 5 percent, . . . , 50 percent,51 percent, 52 percent, . . . , 95 percent, 96 percent, 97 percent, 98percent, 99 percent, or 100 percent. Moreover, any numerical rangedefined by two R numbers as defined in the above is also specificallydisclosed.

DESCRIPTION OF EMBODIMENTS

Provided herein are lubricating oil compositions comprising:

i) a major amount of a base oil,

ii) at least one oil-soluble molybdenum compound and

iii) a zinc dialkyldithiophosphate compound,

wherein the molybdenum content derived from the molybdenum compound isat least about 10 ppm based on the total weight of the lubricating oilcomposition and the phosphorus content derived from the zincdialkyldithiophosphate compound is 200 to 500 ppm based on the totalweight of the lubricating oil composition.

In certain embodiments, the phosphorus content of the composition isabout 200 to 500 ppm. In other embodiments, the phosphorus content ofthe composition is about 250 to 400 ppm, about 300 to 400 ppm. Incertain embodiments, the SAE viscosity of the composition is 5W-20.

i). The Base Oil of Lubricating Viscosity

The lubricating oil compositions disclosed herein generally comprise atleast one oil of lubricating viscosity. Any base oil known to a skilledartisan can be used as the oil of lubricating viscosity disclosedherein. Some base oils suitable for preparing the lubricating oilcompositions have been described in Mortier et al., “Chemistry andTechnology of Lubricants,” 2nd Edition, London, Springer, Chapters 1 and2 (1996); and A. Sequeria, Jr., “Lubricant Base Oil and Wax Processing,”New York, Marcel Decker, Chapter 6, (1994); and D. V. Brock, LubricationEngineering, Vol. 43, pages 184-5, (1987), all of which are incorporatedherein by reference. Generally, the amount of the base oil in thelubricating oil composition may be from about 50 to about 99.5 wt. %,based on the total weight of the lubricating oil composition. In someembodiments, the amount of the base oil in the lubricating oilcomposition is from about 75 to about 99 wt. %, from about 80 to about98.5 wt. %, or from about 80 to about 98 wt. %, based on the totalweight of the lubricating oil composition. In certain embodiments, theamount of base oil in the lubricant oil compositions provided herein isabout 45%, 50%, 52%, 54%, 56%, 58%, 60%, 62%, 64%, 66%, 68%, 70%, 75%,80%, 85% or about 90% by total weight of the composition.

In certain embodiments, the base oil is or comprises any natural orsynthetic lubricating base oil fraction. Some non-limiting examples ofsynthetic oils include oils, such as polyalphaolefins or PAOs, preparedfrom the polymerization of at least one alpha-olefin, such as ethylene,or from hydrocarbon synthesis procedures using carbon monoxide andhydrogen gases, such as the Fisher-Tropsch process. In certainembodiments, the base oil comprises less than about 10 wt. % of one ormore heavy fractions, based on the total weight of the base oil. A heavyfraction refers to a lube oil fraction having a viscosity of at leastabout 20 cSt at 100° C. In certain embodiments, the heavy fraction has aviscosity of at least about 25 cSt or at least about 30 cSt at 100° C.In further embodiments, the amount of the one or more heavy fractions inthe base oil is less than about 10 wt. %, less than about 5 wt. %, lessthan about 2.5 wt. %, less than about 1 wt. %, or less than about 0.1wt. %, based on the total weight of the base oil. In still furtherembodiments, the base oil comprises no heavy fraction.

In certain embodiments, the lubricating oil compositions comprise amajor amount of a base oil of lubricating viscosity. In someembodiments, the base oil has a kinematic viscosity at 100° C. fromabout 2 centistokes (cSt) to about 20 cSt, from about 4 centistokes(cSt) to about 16 cSt, or from about 5 cSt to about 13 cSt. Thekinematic viscosity of the base oils or the lubricating oil compositionsdisclosed herein can be measured according to ASTM D 445, which isincorporated herein by reference.

In other embodiments, the base oil is or comprises a base stock or blendof base stocks. In further embodiments, the base stocks are manufacturedusing a variety of different processes including, but not limited to,distillation, solvent refining, hydrogen processing, oligomerization,esterification, and rerefining. In some embodiments, the base stockscomprise a rerefined stock. In further embodiments, the rerefined stockshall be substantially free from materials introduced throughmanufacturing, contamination, or previous use.

In some embodiments, the base oil comprises one or more of the basestocks in one or more of Groups I-V as specified in the AmericanPetroleum Institute (API) Publication 1509, Fourteen Edition, December1996 (i.e., API Base Oil Interchangeability Guidelines for Passenger CarMotor Oils and Diesel Engine Oils), which is incorporated herein byreference. The API guideline defines a base stock as a lubricantcomponent that may be manufactured using a variety of differentprocesses. Groups I, II and III base stocks are mineral oils, each withspecific ranges of the amount of saturates, sulfur content and viscosityindex. Group IV base stocks are polyalphaolefins (PAO). Group V basestocks include all other base stocks not included in Group I, II, III,or IV.

The saturates levels, sulfur levels and viscosity indices for Group I,II, III, IV and V base stocks are listed in Table 1 below.

TABLE 1 Sulfur (As Viscosity Index (As determined Saturates (Asdetermined determined by by ASTM D 4294, ASTM D Group by ASTM D 2007)ASTM D 2270) 4297 or ASTM D 3120) I Less than 90% saturates. Greaterthan or Greater than or equal to 80 and equal to 0.03% less than 120.sulfur. II Greater than or equal to Less than or equal Greater than orequal to 80 and 90% saturates. to 0.03% sulfur. less than 120. IIIGreater than or equal to Less than or equal Greater than or equal to120. 90% saturates. to 0.03% sulfur. IV Defined as polyalphaolefins(PAO) V All other base stocks not included in Groups I, II, III or IV

In some embodiments, the base oil comprises one or more of the basestocks in Group I, II, III, IV, V or a combination thereof. In otherembodiments, the base oil comprises one or more of the base stocks inGroup II, III, IV or a combination thereof. In further embodiments, thebase oil comprises one or more of the base stocks in Group II, III, IVor a combination thereof wherein the base oil has a kinematic viscosityfrom about 2.5 centistokes (cSt) to about 20 cSt, from about 4 cSt toabout 20 cSt, or from about 5 cSt to about 16 cSt at 100° C.

The base oil may be selected from the group consisting of natural oilsof lubricating viscosity, synthetic oils of lubricating viscosity andmixtures thereof. In some embodiments, the base oil includes base stocksobtained by isomerization of synthetic wax and slack wax, as well ashydrocrackate base stocks produced by hydrocracking (rather than solventextracting) the aromatic and polar components of the crude. In otherembodiments, the base oil of lubricating viscosity includes naturaloils, such as animal oils, vegetable oils, mineral oils (e.g., liquidpetroleum oils and solvent treated or acid-treated mineral oils of theparaffinic, naphthenic or mixed paraffinic-naphthenic types), oilsderived from coal or shale, and combinations thereof. Some non-limitingexamples of animal oils include bone oil, lanolin, fish oil, lard oil,dolphin oil, seal oil, shark oil, tallow oil, and whale oil. Somenon-limiting examples of vegetable oils include castor oil, olive oil,peanut oil, rapeseed oil, corn oil, sesame oil, cottonseed oil, soybeanoil, sunflower oil, safflower oil, hemp oil, linseed oil, tung oil,oiticica oil, jojoba oil, and meadow foam oil. Such oils may bepartially or fully hydrogenated.

In some embodiments, the synthetic oils of lubricating viscosity includehydrocarbon oils and halo-substituted hydrocarbon oils such aspolymerized and inter-polymerized olefins, alkylbenzenes, polyphenyls,alkylated diphenyl ethers, alkylated diphenyl sulfides, as well as theirderivatives, analogues and homologues thereof, and the like. In otherembodiments, the synthetic oils include alkylene oxide polymers,interpolymers, copolymers and derivatives thereof wherein the terminalhydroxyl groups can be modified by esterification, etherification, andthe like. In further embodiments, the synthetic oils include the estersof dicarboxylic acids with a variety of alcohols. In certainembodiments, the synthetic oils include esters made from C₅ to C₁₂monocarboxylic acids and polyols and polyol ethers. In furtherembodiments, the synthetic oils include tri-alkyl phosphate ester oils,such as tri-n-butyl phosphate and tri-iso-butyl phosphate.

In some embodiments, the synthetic oils of lubricating viscosity includesilicon-based oils (such as the polyakyl-, polyaryl-, polyalkoxy-,polyaryloxy-siloxane oils and silicate oils). In other embodiments, thesynthetic oils include liquid esters of phosphorus-containing acids,polymeric tetrahydrofurans, polyalphaolefins, and the like.

Base oil derived from the hydroisomerization of wax may also be used,either alone or in combination with the aforesaid natural and/orsynthetic base oil. Such wax isomerate oil is produced by thehydroisomerization of natural or synthetic waxes or mixtures thereofover a hydroisomerization catalyst.

In further embodiments, the base oil comprises a poly-alpha-olefin(PAO). In general, the poly-alpha-olefins may be derived from analpha-olefin having from about 2 to about 30, from about 4 to about 20,or from about 6 to about 16 carbon atoms. Non-limiting examples ofsuitable poly-alpha-olefins include those derived from octene, decene,mixtures thereof, and the like. These poly-alpha-olefins may have aviscosity from about 2 to about 15, from about 3 to about 12, or fromabout 4 to about 8 centistokes at 100° C. In some instances, thepoly-alpha-olefins may be used together with other base oils such asmineral oils.

In further embodiments, the base oil comprises a polyalkylene glycol ora polyalkylene glycol derivative, where the terminal hydroxyl groups ofthe polyalkylene glycol may be modified by esterification,etherification, acetylation and the like. Non-limiting examples ofsuitable polyalkylene glycols include polyethylene glycol, polypropyleneglycol, polyisopropylene glycol, and combinations thereof. Non-limitingexamples of suitable polyalkylene glycol derivatives include ethers ofpolyalkylene glycols (e.g., methyl ether of polyisopropylene glycol,diphenyl ether of polyethylene glycol, diethyl ether of polypropyleneglycol, etc.), mono- and polycarboxylic esters of polyalkylene glycols,and combinations thereof. In some instances, the polyalkylene glycol orpolyalkylene glycol derivative may be used together with other base oilssuch as poly-alpha-olefins and mineral oils.

In further embodiments, the base oil comprises any of the esters ofdicarboxylic acids (e.g., phthalic acid, succinic acid, alkyl succinicacids, alkenyl succinic acids, maleic acid, azelaic acid, suberic acid,sebacic acid, fumiaric acid, adipic acid, linoleic acid dimer, malonicacid, alkyl malonic acids, alkenyl malonic acids, and the like) with avariety of alcohols (e.g., butyl alcohol, hexyl alcohol, dodecylalcohol, 2-ethylhexyl alcohol, ethylene glycol, diethylene glycolmonoether, propylene glycol, and the like). Non-limiting examples ofthese esters include dibutyl adipate, di(2-ethylhexyl) sebacate,di-n-hexyl fumarate, dioctyl sebacate, diisooctyl azelate, diisodecylazelate, dioctyl phthalate, didecyl phthalate, dieicosyl sebacate, the2-ethylhexyl diester of linoleic acid dimer, and the like.

In further embodiments, the base oil comprises a hydrocarbon prepared bythe Fischer-Tropsch process. The Fischer-Tropsch process prepareshydrocarbons from gases containing hydrogen and carbon monoxide using aFischer-Tropsch catalyst. These hydrocarbons may require furtherprocessing in order to be useful as base oils. For example, thehydrocarbons may be dewaxed, hydroisomerized, and/or hydrocracked usingprocesses known to a person of ordinary skill in the art.

In further embodiments, the base oil comprises an unrefined oil, arefined oil, a rerefined oil, or a mixture thereof. Unrefined oils arethose obtained directly from a natural or synthetic source withoutfurther purification treatment. Non-limiting examples of unrefined oilsinclude shale oils obtained directly from retorting operations,petroleum oils obtained directly from primary distillation, and esteroils obtained directly from an esterification process and used withoutfurther treatment. Refined oils are similar to the unrefined oils exceptthe former have been further treated by one or more purificationprocesses to improve one or more properties. Many such purificationprocesses are known to those skilled in the art such as solventextraction, secondary distillation, acid or base extraction, filtration,percolation, and the like. Rerefined oils are obtained by applying torefined oils processes similar to those used to obtain refined oils.Such rerefined oils are also known as reclaimed or reprocessed oils andoften are additionally treated by processes directed to removal of spentadditives and oil breakdown products.

ii). Oil Soluble Molybdenum Compounds

For the lubricating oil compositions provided herein, any suitableoil-soluble molybdenum compound can be employed. Exemplary of suchoil-soluble molybdenum compounds include, but are not limited todithiocarbamates, dithiophosphates, dithiophosphinates, xanthates,thioxanthates, sulfides, and the like, and mixtures thereof. In certainembodiments, the molybdenum compounds are molybdenum dithiocarbamates,dialkyldithiophosphates, alkyl xanthates and alkylthioxanthates.

The molybdenum compound may be mono-, di-, tri- or tetra-nuclear. Incertain embodiments, the compound is a dinuclear or trinuclearmolybdenum compound. In one embodiment, the molybdenum compound is anorgano-molybdenum compound. In another embodiment, the molybdenumcompound is selected from the group consisting of molybdenumdithiocarbamates (MoDTC), molybdenum dithiophosphates, molybdenumdithiophosphinates, molybdenum xanthates, molybdenum thioxanthates,molybdenum sulfides and mixtures thereof. In another embodiment, themolybdenum compound is present as a molybdenum dithiocarbamate or atrinuclear organo-molybdenum compound. In one embodiment, theoil-soluble molybdenum compound is selected from molybdenumdithiocarbamate, molybdenum-succinimide complex and a mixture thereof.

In certain aspects, the molybdenum compound may be an acidic molybdenumcompound. These compounds will react with a basic nitrogen compound asmeasured by ASTM test D-664 or D-2896 titration procedure and aretypically hexavalent. Examples of such compounds include molybdic acid,ammonium molybdate, sodium molybdate, potassium molybdate, and otheralkaline metal molybdates and other molybdenum salts, e.g., hydrogensodium molybdate, MoOCl₄, MoO₂Br₂, Mo₂O₃Cl₆, molybdenum trioxide orsimilar acidic molybdenum compounds. Alternatively, the compositionsherein comprise molybdenum/sulfur complexes of basic nitrogen compoundsas described, for example, in U.S. Pat. Nos. 4,263,152; 4,285,822;4,283,295; 4,272,387; 4,265,773; 4,261,843; 4,259,195; 4,259,194 and6,562,765; and WO 94/06897.

The basic nitrogen compound used to prepare the oxymolybdenum compoundsfor use herein have at least one basic nitrogen and are, in certainembodiments, oil-soluble. Typical examples of such compositions aresuccinimides, carboxylic acid amides, hydrocarbyl monoamines,hydrocarbon polyamines, Mannich bases, phosphoramides,thiophosphoramides, phosphonamides, dispersant viscosity indeximprovers, and mixtures thereof. Any of the nitrogen-containingcompositions may be after-treated with, e.g., boron, using procedureswell known in the art so long as the compositions continue to containbasic nitrogen. These after-treatments are particularly applicable tosuccinimides and Mannich base compositions.

The mono and polysuccinimides that can be used to prepare the molybdenumcomplexes described herein are disclosed in numerous references and arewell known in the art. Certain exemplary succinimides and the relatedmaterials are described in U.S. Pat. Nos. 3,219,666; 3,172,892; and3,272,746, the disclosures of which are hereby incorporated byreference. The term “succinimide” is understood in the art to includemany of the amide, imide, and amidine species which may also be formed.The predominant product however is a succinimide and this term has beengenerally accepted as meaning the product of a reaction of an alkenylsubstituted succinic acid or anhydride with a nitrogen-containingcompound. In certain embodiments, succinimides for use herein arecommercial available succinimides, such as those prepared from ahydrocarbyl succinic anhydride, wherein the hydrocarbyl group containsfrom about 24 to about 350 carbon atoms, and an ethylene amine, saidethylene amines being characterized by ethylene diamine, diethylenetriamine, triethylene tetramine, and tetraethylene pentamine. In oneembodiment, the succinimides include succinimides prepared frompolyisobutenyl succinic anhydride of 70 to 128 carbon atoms andtetraethylene pentamine or triethylene tetramine or mixtures thereof.

Also included in the succinimides are the cooligomers of a hydrocarbylsuccinic acid or anhydride and a poly secondary amine containing atleast one tertiary amino nitrogen in addition to two or more secondaryamino groups. In certain embodiments, the cooligomers have an averagemolecular weight between 1,500 and 50,000. In one embodiment, themolybdenum compound for use in the compositions herein is prepared byreacting polyisobutenyl succinic anhydride and ethylene dipiperazine.

In certain embodiment, carboxylic acid amide compositions are alsosuitable starting materials for preparing the oxymolybdenum compoundsused herein. Typical of such compounds are those disclosed in U.S. Pat.No. 3,405,064, the disclosure of which is hereby incorporated byreference. These compositions can be prepared by reacting a carboxylicacid or anhydride or ester thereof, having at least 12 to about 350aliphatic carbon atoms in the principal aliphatic chain and, if desired,having sufficient pendant aliphatic groups to render the molecule oilsoluble with an amine or a hydrocarbyl polyamine, such as an ethyleneamine, to give a mono or polycarboxylic acid amide. In one embodiment,the amides are prepared from (1) a carboxylic acid of the formulaR′COOH, where R′ is C₁₂₋₂₀ alkyl or a mixture of this acid with apolyisobutenyl carboxylic acid in which the polyisobutenyl groupcontains from 72 to 128 carbon atoms and (2) an ethylene amine,especially triethylene tetramine or tetraethylene pentamine or mixturesthereof.

Another class of compounds which can be used to prepare molybdenumcompounds are hydrocarbyl monoamines and hydrocarbyl polyamines, such asthose disclosed in U.S. Pat. No. 3,574,576, the disclosure of which ishereby incorporated by reference. The hydrocarbyl group, for examplealkyl, or olefinic having one or two sites of unsaturation, usuallycontains from 9 to 350, preferably from 20 to 200 carbon atoms.Exemplary of such hydrocarbyl polyamines are those which are derived,e.g., by reacting polyisobutenyl chloride and a polyalkylene polyamine,such as an ethylene amine, e.g., ethylene diamine, diethylene triamine,tetraethylene pentamine, 2-aminoethylpiperazine, 1,3-propylene diamine,1,2-propylenediamine, and the like.

Another class of compounds useful for supplying basic nitrogen are theMannich base compositions. These compositions are prepared from a phenolor C₉₋₂₀₀ alkylphenol, an aldehyde, such as formaldehyde or formaldehydeprecursor such as paraformaldehyde, and an amine compound. The amine maybe a mono or polyamine and typical compositions are prepared from analkylamine, such as methylamine or an ethylene amine, such as,diethylene triamine, or tetraethylene pentamine, and the like. Thephenolic material may be sulfurized and preferably is dodecylphenol or aC₈₀₋₁₀₀ alkylphenol. Typical Mannich bases which can be used aredisclosed in U.S. Pat. Nos. 4,157,309 and 3,649,229; 3,368,972; and3,539,663, the disclosures of which are hereby incorporated byreference.

Another class of composition useful for preparing the oxymolybdenumcomplexes employed in the lubricating oil compositions provided hereinare the phosphoramides and phosphonamides such as those disclosed inU.S. Pat. Nos. 3,909,430 and 3,968,157, the disclosures of which arehereby incorporated by reference. These compositions may be prepared byforming a phosphorus compound having at least one P—N bond. They can beprepared, for example, by reacting phosphorus oxychloride with ahydrocarbyl diol in the presence of a monoamine or by reactingphosphorus oxychloride with a difunctional secondary amine and amono-functional amine. Thiophosphoramides can be prepared by reacting anunsaturated hydrocarbon compound containing from 2 to 450 or more carbonatoms, such as polyethylene, polyisobutylene, polypropylene, ethylene,1-hexene, 1,3-hexadiene, isobutylene, 4-methyl-1-pentene, and the like,with phosphorus pentasulfide and a nitrogen-containing compound asdefined above, particularly an alkylamine, alkyldiamine, alkylpolyamine,or an alkyleneamine, such as ethylene diamine, diethylenetriamine,triethylenetetramine, tetraethylenepentamine, and the like.

Further molybdenum compounds useful in the compositions provided hereinare organo-molybdenum compounds of the formulae

Mo(ROCS₂)₄ and

Mo(RSCS₂)₄

wherein R is an organic group selected from the group consisting ofalkyl, aryl, aralkyl and alkoxyalkyl, generally of from 1 to 30 carbonatoms, and in one embodiment, from 2 to 12 carbon atoms and in anotherembodiment, alkyl of 2 to 12 carbon atoms.

In one embodiment, the molybdenum compounds are dithiocarbamates ofmolybdenum represented by the formula:

wherein, R₁, R₂, R₃ and R₄ are each independently a straight-chain orbranched-chain alkyl group or a straight-chain or branched-chain alkenylgroup having four to eighteen carbons; and X₁, X₂, X₃ and X₄ are eachindependently an oxygen atom or a sulfur atom, the ratio between thenumber of the oxygen atom or atoms and that of the sulfur atom or atomswith respect to X₁ through X₄ being 1/3 to 3/1. In one embodiment, R₁,R₂, R₃ and R₄, are each alkyl. In one embodiment, the alkyl is butyl,2-ethylhexyl, isotridecyl or stearyl. The R₁, R₂, R₃ and R₄ groups inone molybdenum dithiocarbamate may be identical with or different fromeach other. Further, two or more molybdenum dithiocarbamates havingdifferent R₁, R₂, R₃ and R₄ groups may be used in a mixed state.

In one embodiment, organo-molybdenum compounds useful in the lubricatingcompositions herein are trinuclear molybdenum compounds, including thoseof the formula Mo₃S_(k)L_(n)Q_(z) and mixtures thereof, wherein L areindependently selected ligands having organic groups with a sufficientnumber of carbon atoms to render the compound soluble or dispersible inthe oil, n is from 1 to 4, k varies from 4 through 7, Q is selected fromthe group of neutral electron donating compounds such as water, amines,alcohols, phosphines, and ethers, and z ranges from 0 to 5 and includesnon-stoichiometric values. In certain embodiments, at least 21 totalcarbon atoms are present among all the ligands' organic groups, such asat least 25, at least 30, or at least 35 carbon atoms.

The ligands are independently selected from the group of:

and mixtures thereof, wherein X, X₁, X₂, and Y are independentlyselected from the group of oxygen and sulfur, and wherein R₁, R₂, and Rare each independently selected from hydrogen and organic groups thatmay be the same or different. In one embodiment, the organic groups arehydrocarbyl groups such as alkyl (e.g., in which the carbon atomattached to the remainder of the ligand is primary or secondary), aryl,substituted aryl and ether groups. In one embodiment, each ligand hasthe same hydrocarbyl group.

The term “hydrocarbyl” denotes a substituent having carbon atomsdirectly attached to the remainder of the ligand and is predominantlyhydrocarbyl in character, exemplary substituents include the following:

1. Hydrocarbon substituents, that is, aliphatic (for example alkyl oralkenyl), alicyclic (for example cycloalkyl or cycloalkenyl)substituents, aromatic-, aliphatic- and alicyclic-substituted aromaticnuclei and the like, as well as cyclic substituents wherein the ring iscompleted through another portion of the ligand (that is, any twoindicated substituents may together form an alicyclic group).

2. Substituted hydrocarbon substituents, that is, those containingnon-hydrocarbon groups which do not alter the predominantly hydrocarbylcharacter of the substituent. Those skilled in the art are aware ofsuitable groups (e.g., halo, especially chloro and fluoro, amino,alkoxyl, mercapto, alkylmercapto, nitro, nitroso, sulfoxy, and thelike).

3. Hetero substituents, that is, substituents which, while predominantlyhydrocarbon in character, contain atoms other than carbon present in achain or ring otherwise composed of carbon atoms.

In certain embodiments, the organic groups of the ligands have asufficient number of carbon atoms to render the compound soluble ordispersible in the oil. For example, the number of carbon atoms in eachgroup will generally range between about 1 to about 100, from about 1 toabout 30 or between about 4 to about 20. In certain embodiments, theligands include dialkyldithiophosphate, alkylxanthate, anddialkyldithiocarbamate. In one embodiment, the ligand isdialkyldithiocarbamate. Organic ligands containing two or more of theabove flnctionalities can also serve as ligands by binding to one ormore of the cores. Those skilled in the art will realize that formationof the compounds provided herein requires selection of ligands havingthe appropriate charge to balance the core's charge.

Compounds having the formula Mo₃S_(k)L_(n)Q_(z) to have cationic coressurrounded by anionic ligands and are represented by structures such as

and have net charges of +4. Consequently, in order to solubilize thesecores the total charge among all the ligands must be −4. In oneembodiment, four monoanionic ligands are present. Without wishing to bebound by any theory, it is believed that two or more trinuclear coresmay be bound or interconnected by means of one or more ligands and theligands may be multidentate. This includes the case of a multidentateligand having multiple connections to a single core. It is believed thatoxygen and/or selenium may be substituted for sulfur in the core(s).

Oil-soluble or dispersible trinuclear molybdenum compounds can beprepared by reacting in the appropriate liquid(s)/solvent(s) amolybdenum source such as (NH₄)₂Mo₃S₁₃.n(H₂O), where n varies between 0and 2 and includes non-stoichiometric values, with a suitable ligandsource such as a tetralkylthiuram disulfide. Other oil-soluble ordispersible trinuclear molybdenum compounds can be formed during areaction in the appropriate solvent(s) of a molybdenum source such as of(NH₄)₂Mo₃S₁₃.n(H₂O), a ligand source such as tetralkylthiuram disulfide,dialkyldithiocarbamate, or dialkyldithiophosphate, and a sulfurabstracting agent such as cyanide ions, sulfite ions, or substitutedphosphines. Alternatively, a trinuclear molybdenum-sulfur halide saltsuch as [M′]2 [Mo₃S₇A6], where M′ is a counter ion, and A is a halogensuch as Cl, Br, or I, may be reacted with a ligand source such as adialkyldithiocarbamate or dialkyldithiophosphate in the appropriateliquid(s)/solvent(s) to form an oil-soluble or dispersible trinuclearmolybdenum compound. The appropriate liquid/solvent may be, for example,aqueous or organic.

A compound's oil solubility or dispersibility may be influenced by thenumber of carbon atoms in the ligand's organic groups. In the compoundsherein, at least 21 total carbon atoms should be present among all theligands' organic groups. In certain embodiments, the ligand sourcechosen has a sufficient number of carbon atoms in its organic groups torender the compound soluble or dispersible in the lubricatingcomposition.

The terms “oil-soluble” or “dispersible” used herein do not necessarilyindicate that the compounds or additives are soluble, dissolvable,miscible, or capable of being suspended in the oil in all proportions.These do mean, however, that they are, for instance, soluble or stablydispersible in oil to an extent sufficient to exert their intendedeffect in the environment in which the oil is employed. Moreover, theadditional incorporation of other additives may also permitincorporation of higher levels of a particular additive, if desired.

The lubricating compositions provided herein contain the molybdenumcompound at a concentration of at least about 10 ppm in terms ofmolybdenum content. In certain embodiments, the molybdenum compound isat a concentration from about 10 ppm to about 10,000 ppm in terms ofmolybdenum content. In certain embodiments, the molybdenum compound at aconcentration from about 50 to 1500 ppm, or about 250 to 1200 ppm interms of molybdenum content. In one embodiment, the molybdenum compoundis at a concentration of about 10 ppm, 50 ppm, 100 ppm, 250 ppm, 500ppm, 750 ppm, or 1000 ppm in terms of molybdenum content.

The amount of molybdenum may be determined by Inductively Coupled Plasma(ICP) emission spectroscopy using the method described in ASTM D5185.

iii). Zinc Dialkyldithiophosphate Compounds

The lubricating oil compositions provided herein additionally contain azinc dialkyldithiophosphate compound. The alkyl group in the zincdialkyldithiophosphate compound is, for example, branched ornon-branched alkyl containing 3 to 30 carbon atoms. In anotherembodiment, the alkyl group has 3 to 8 carbon atoms. Examples of alkylgroups include a straight or branched ethyl, propyl, butyl, pentyl,methylpentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl,tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, and octadecylgroups.

These zinc dialkyldithiophosphate salts can be prepared in accordancewith known techniques by first forming a dihydrocarbyl dithiophosphoricacid (DDPA), usually by reaction of one or more alcohol or a phenol withP₂S₅ and then neutralizing the formed DDPA with a zinc compound. Forexample, a dithiophosphoric acid may be made by reacting mixtures ofprimary and secondary alcohols. Alternatively, multiple dithiophosphoricacids can be prepared where the hydrocarbyl groups on one are entirelysecondary in character and the hydrocarbyl groups on the others areentirely primary in character. To make the zinc salt, any basic orneutral zinc compound could be used but the oxides, hydroxides andcarbonates are most often employed. Commercial additives frequentlycontain an excess of zinc due to the use of an excess of the basic zinccompound in the neutralization reaction.

In one embodiment, the oil soluble zinc dialkyldithiophosphates may beproduced from dialkykyldithiophosphoric acids (DDPA) of the formula:

The hydroxyl alkyl compounds from which the dialkyldithiophosphoricacids are derived can be represented generically by the formula ROH orR′OH, wherein R or R′ is alkyl or substituted alkyl, in one embodiment,branched or non-branched alkyl containing 3 to 30 carbon atoms. Inanother embodiment, R or R′ is a branched or non-branched alkylcontaining 3 to 8 carbon atoms. Examples of alkyl groups include astraight or branched ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl,nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl,hexadecyl, heptadecyl, and octadecyl groups.

In certain embodiments, the dialkyldithiophosphoric acids are preparedfrom mono-, di-, tri-, tetra-, and other polyhydroxy alkyl compounds, ormixtures of two or more of the foregoing. In one embodiment, the zincdialkyldithiophosphate is derived from a single primary alcohol. In oneembodiment, the single primary alcohol is 2-ethylhexanol. In oneembodiment, the zinc dialkyldithiophosphate is derived from one or moresecondary alkyl alcohols. In one embodiment, the mixture of secondaryalcohols is a mixture of 2-butanol and 4-methyl-2-pentanol.

The zinc salts can be prepare from the dihydrocarbyl dithiophosphoricacids by reacting with a zinc compound. In some embodiments, a basic ora neutral zinc compound is used. In other embodiments, an oxide,hydroxide or carbonate of zinc is used.

The phosphorus pentasulfide reactant used in the dialkyldithiophosphoricacid formation step may contain certain amounts of one or more of P₂S₃,P₄S₃, P₄S₇, or P₄S₉. Compositions as such may also contain minor amountsof free sulfur. In certain embodiments, the phosphorus pentasulfidereactant is substantially free of any of P₂S₃, P₄S₃, P₄S₇, and P₄S₉. Incertain embodiments, the phosphorus pentasulfide reactant issubstantially free of free sulfur.

The phosphorus content derived from the zinc dialkyldithiophosphatecompound is about 200 to 500 ppm based on the total weight of thelubricating oil composition. In certain embodiments, the phosphoruscontent derived from the zinc dialkyldithiophosphate compound is about200 to 400 ppm. In one embodiment, the phosphorus content derived fromthe zinc dialkyldithiophosphate compound is about 200, 250, 300, 350,400, 450, 500 ppm. In one embodiment, phosphorus content derived fromthe zinc dialkyldithiophosphate compound is about 250 ppm.

The following additive components are examples of some of the componentsthat can be favorably employed in the present invention. These examplesof additives are provided to illustrate the present invention, but theyare not intended to limit it:

1) Metal Detergents

In some embodiments, the lubricating oil composition provided hereincomprises at least a neutral or overbased metal detergent as anadditive, or additive components. In certain embodiments, the metaldetergents in lubricating oil compositions acts as a neutralizer ofacidic products within the oil. In certain embodiments, the metaldetergent prevents the formation of deposits on the surface of anengine. Depending on the nature of the acid used, the detergent may haveadditional functions, for example, antioxidant properties. In certainaspects, lubricating oil compositions contain metal detergentscomprising either overbased detergents or mixtures of neutral andoverbased detergents. The term “overbased” is intended to defineadditives which contain a metal content in excess of that required bythe stoichiometry of the particular metal and the particular organicacid used. The excess metal exists in the form of particles of inorganicbase, e.g. a hydroxide or carbonate, surrounded by a sheath of metalsalt. The sheath serves to maintain the particles in dispersion in aliquid oleaginous vehicle. The amount of excess metal is commonlyexpressed as the ratio of total equivalence of excess metal toequivalence of organic acid and is typically 0.1 to 30.

Some non-limiting examples of suitable metal detergents includesulfurized or unsulfurized alkyl or alkenyl phenates, alkyl or alkenylaromatic sulfonates, borated sulfonates, sulfurized or unsulfurizedmetal salts of multi-hydroxy alkyl or alkenyl aromatic compounds, alkylor alkenyl hydroxy aromatic sulfonates, sulfurized or unsulfurized alkylor alkenyl naphthenates, metal salts of alkanoic acids, metal salts ofan alkyl or alkenyl multiacid, and chemical and physical mixturesthereof. Other non-limiting examples of suitable metal detergentsinclude metal sulfonates, phenates, salicylates, phosphonates,thiophosphonates and combinations thereof. The metal can be any metalsuitable for making sulfonate, phenate, salicylate or phosphonatedetergents. Non-limiting examples of suitable metals include alkalimetals, alkaline metals and transition metals. In some embodiments, themetal is Ca, Mg, Ba, K, Na, Li or the like. An exemplary metal detergentwhich may be employed in the lubricating oil compositions includesoverbased calcium phenate.

Generally, the amount of the metal detergent additive can be less than10000 ppm, less than 1000 ppm, less than 100 ppm, or less than 10 ppm,based on the total weight of the lubricating oil composition. In someembodiments, the amount of the metal detergent is from about 0.001 wt. %to about 5 wt. %, from about 0.05 wt. % to about 3 wt. %, or from about0.1 wt. % to about 1 wt. %, based on the total weight of the lubricatingoil composition. Some suitable detergents have been described in Mortieret al., “Chemistry and Technology of Lubricants,” 2nd Edition, London,Springer, Chapter 3, pages 75-85 (1996); and Leslie R. Rudnick,“Lubricant Additives: Chemistry and Applications,” New York, MarcelDekker, Chapter 4, pages 113-136 (2003), both of which are incorporatedherein by reference.

2) Anti Wear and/or Extreme Pressure Agents

In certain embodiments, the lubricating oil compositions disclosedherein can additionally comprise anti wear or extreme pressure agents.Wear occurs in all equipment that has moving parts in contact.Specifically, three conditions commonly lead to wear in engines: (1)surface-to-surface contact; (2) surface contact with foreign matter; and(3) erosion due to corrosive materials. Wear resulting fromsurface-to-surface contact is friction or adhesive wear, from contactwith foreign matter is abrasive wear, and from contact with corrosivematerials is corrosive wear. Fatigue wear is an additional type of wearthat is common in equipment where surfaces are not only in contact butalso experience repeated stresses for prolonged periods. Abrasive wearcan be prevented by installing an efficient filtration mechanism toremove the offending debris. Corrosive wear can be addressed by usingadditives which neutralize the reactive species that would otherwiseattack the metal surfaces. The control of adhesive wear requires the useof additives called antiwear and extreme-pressure (EP) agents.

Under optimal conditions of speed and load, the metal surfaces of theequipment should be effectively separated by a lubricant film.Increasing load, decreasing speed, or otherwise deviating from suchoptimal conditions promote metal-to-metal contact. This contacttypically causes a temperature increase in the contact zone due tofrictional heat, which in turn leads to the loss of lubricant viscosityand hence its film-forming ability. In certain embodiments, antiwearadditive and EP agents offer protection by a similar mechanism. Incertain embodiments, EP additives require higher activation temperaturesand load than antiwear additives.

Without being bound to any particular theory, it is believed thatantiwear and/or EP additives function by thermal decomposition and byforming products that react with the metal surface to form a solidprotective layer. This solid metal film fills the surface asperities andfacilitates effective film formation, thereby reducing friction andpreventing welding and surface wear.

Most antiwear and extreme pressure agents contain sulfur, chlorine,phosphorus, boron, or combinations thereof. The classes of compoundsthat inhibit adhesive wear include, for example, alkyl and aryldisulfides and polysulfides; dithiocarbamates; chlorinated hydrocarbons;and phosphorus compounds such as alkyl phosphites, phosphates,dithiophosphates, and alkenylphosphonates.

Exemplary antiwear agents that can be included in the lubricant oilcompositions provided herein include metal (e.g., Pb, Sb, and the like)salts of dithiophosphate, metal (e.g., Pb, Sb, and the like) salts ofdithiocarbamate, metal (e.g., Pb, Sb and the like) salts of fatty acids,boron compounds, phosphate esters, phosphite esters, amine salts ofphosphoric acid esters or thiophosphoric acid esters, reaction productsof dicyclopentadiene and thiophosphoric acids and combinations thereof.The amount of the anti-wear agent may vary from about 0.01 wt. % toabout 5 wt. %, from about 0.05 wt. % to about 3 wt. %, or from about 0.1wt. % to about 1 wt. %, based on the total weight of the lubricating oilcomposition. Some suitable anti-wear agents have been described inLeslie R. Rudnick, “Lubricant Additives: Chemistry and Applications,”New York, Marcel Dekker, Chapter 8, pages 223-258 (2003), which isincorporated herein by reference.

In one embodiment, the sulfated ash content of the total lubricating oilcomposition is less than 5 wt. %, less than 4 wt. %, less than 3 wt. %,less than 2 wt. %, or less than 1 wt. %, as measured according to ASTMD874.

In one embodiment, the EP agents for use in the lubricant oilcompositions include alkyl and aryl disulfides and polysulfides,dithiocarbamates, chlorinated hydrocarbons, dialkyl hydrogen phosphites,and salts of alkyl phosphoric acids. Methods of making these EP agentsare known in the art. For example, polysulfides are synthesized fromolefins either by reacting with sulfur or sulfur halides, followed bydehydrohalogenation. Dialkydithiocarbamates are prepared either byneutralizing dithiocarbamic acid (which can be prepared by reacting adiakylamine and carbon disulfide at low temperature) with bases, such asantimony oxided, or by its addition to activated olefins, such as alkylacrylates.

In certain embodiments, the lubricating oil compositions comprise one ormore EP agents. In one embodiment, use of more that one EP agent leadsto synergism. For example, synergism may be observed between sulfur andchlorine-containing EP agents. An exemplary lubricating oil compositionprovided herein includes one or more EP agents selected from: zincdialkyldithiophosphate (primary alkyl type & secondary alkyl type),sulfurized oils, diphenyl sulfide, methyl trichlorostearate, chlorinatednaphthalene, fluoroalkylpolysiloxane, and lead naphthenate.

3. Rust Inhibitors (Anti Rust Agents)

Protection against rust is an important consideration in formulatinglubricants. Without protection, rust ultimately causes a loss of metal,thereby lowering the integrity of the equipment, and resulting in enginemal-function. In addition, corrosion exposes fresh metal that can wearat an accelerated rate, perpetuated by the metal ions that might bereleased into the fluid and act as oxidation promoters.

The lubricating oil composition disclosed herein can optionally comprisea rust inhibitor that can inhibit the corrosion of metal surfaces. Anyrust inhibitor known by a person of ordinary skill in the art may beused in the lubricating oil composition. The rust inhibitors attachthemselves to metal surfaces to form an impenetrable protective film,which can be physically or chemically adsorbed to the surface.Specifically, film formation occurs when the additives interact with themetal surface via their polar ends and associate with the lubricant viatheir nonpolar ends. Suitable rust inhibitors may include, for example,various nonionic polyoxyethylene surface active agents such aspolyoxyethylene lauryl ether, polyoxyethylene higher alcohol ether,polyoxyethylene nonylphenyl ether, polyoxyethylene octylphenyl ether,polyoxyethylene octyl stearyl ether, polyoxyethylene oleyl ether,polyoxyethylene sorbitol monostearate, polyoxyethylene sorbitolmono-oleate, and polyethylene glycol monooleate. Suitable rustinhibitors may further include other compounds such as, for example,monocarboxylic acids (e.g., 2-ethylhexanoic acid, lauric acid, myristicacid, palmitic acid, oleic acid, linoleic acid, linolenic acid, behenicacid, cerotic acid and the like), oil-soluble polycarboxylic acids(e.g., those produced from tall oil fatty acids, oleic acid, linoleicacid and the like), alkenylsuccinic acids in which the alkenyl groupcontains 10 or more carbon atoms (e.g., tetrapropenylsuccinic acid,tetradecenylsuccinic acid, hexadecenylsuccinic acid, and the like);long-chain alpha,omega-dicarboxylic acids having a molecular weight inthe range of 600 to 3000 daltons and combinations thereof. Furtherexamples of rust agents include metal soaps, fatty acid amine salts,metal salts of heavy sulfonic acid, partial carboxylic acid ester ofpolyhydric alcohol, and phosphoric ester.

4. Demulsifiers

The lubricating oil composition disclosed herein can optionally comprisea demulsifier that can promote oil-water separation in lubricating oilcompositions that are exposed to water or steam. Any demulsifier knownby a person of ordinary skill in the art may be used in the lubricatingoil composition. Non-limiting examples of suitable demulsifiers includeanionic surfactants (e.g., alkyl-naphthalene sulfonates, alkyl benzenesulfonates and the like), nonionic alkoxylated alkylphenol resins,polymers of alkylene oxides (e.g., polyethylene oxide, polypropyleneoxide, block copolymers of ethylene oxide, propylene oxide and thelike), esters of oil soluble acids, polyoxyethylene sorbitan ester andcombinations thereof In certain embodiments, the demulsifiers for useherein include block copolymers of propylene oxide or ethylene oxide andinitiators, such as, for example, glycerol, phenol, formaldehyde resins,soloxanes, polyamines, and polyols. In certain embodiments, the polymerscontain about 20 to about 50% ethylene oxide. These materialsconcentrate at the water-oil interface and create low viscosity zones,thereby promoting droplet coalescence and gravity-driven phaseseparation. Low molecular weight materials, such as, for example, alkalimetal or alkaline earth metal salts of dialkylnaphthalene sulfonicacids, are also useful in certain applications. The amount of thedemulsifier may vary from about 0.01 wt. % to about 10 wt. %, from about0.05 wt. % to about 5 wt. %, or from about 0.1 wt. % to about 3 wt. %,based on the total weight of the lubricating oil composition. Somesuitable demulsifiers have been described in Mortier et al., “Chemistryand Technology of Lubricants,” 2nd Edition, London, Springer, Chapter 6,pages 190-193 (1996), which is incorporated herein by reference.

5. Friction Modifiers

The lubricating oil composition disclosed herein can optionally comprisea friction modifier that can lower the friction between moving parts.Any friction modifier known by a person of ordinary skill in the art maybe used in the lubricating oil composition. They are typicallylong-chain molecules with a polar end group and a nonpolar linearhydrocarbon chain. The polar end groups either physically adsorb ontothe metal surface or chemically react with it, while the hydrocarbonchain extend into the lubricant. The chains associated with one anotherand the lubricant to form a strong lubricant film.

Non-limiting examples of suitable friction modifiers include fattycarboxylic acids; derivatives (e.g., alcohol, esters, borated esters,amides, metal salts and the like) of fatty carboxylic acid; mono-, di-or tri-alkyl substituted phosphoric acids or phosphonic acids;derivatives (e.g., esters, amides, metal salts and the like) of mono-,di- or tri-alkyl substituted phosphoric acids or phosphonic acids;mono-, di- or tri-alkyl substituted amines; mono- or di-alkylsubstituted amides and combinations thereof.

In one embodiment, the friction modifier is a saturated fatty acidcontaining a 13 to 18 carbon chains. The amount of the friction modifiermay vary from about 0.01 wt. % to about 10 wt. %, from about 0.05 wt. %to about 5 wt. %, or from about 0.1 wt. % to about 3 wt. %, based on thetotal weight of the lubricating oil composition. Some suitable frictionmodifiers have been described in Mortier et al., “Chemistry andTechnology of Lubricants,” 2nd Edition, London, Springer, Chapter 6,pages 183-187 (1996); and Leslie R. Rudnick, “Lubricant Additives:Chemistry and Applications,” New York, Marcel Dekker, Chapters 6 and 7,pages 171-222 (2003), both of which are incorporated herein byreference.

6. Pour Point Depressants

The lubricating oil composition disclosed herein can optionally comprisea pour point depressant that can lower the pour point of the lubricatingoil composition. Any pour point depressant known by a person of ordinaryskill in the art may be used in the lubricating oil composition. Incertain embodiments, pour point depressants possess one or morestructural features selected from: (1) polymeric structure; (2) waxy andnon-waxy components; (3) comb structure comprising a short backbone withlong pendant groups; and (4) broad molecular weight distribution.Non-limiting examples of suitable pour point depressants includepolymethacrylates, alkyl acrylate polymers, alkyl methacrylate polymers,alkyl fumarate polymers, di(tetra-paraffin phenol)phthalate, condensatesof tetra-paraffin phenol, condensates of a chlorinated paraffin withnaphthalene, alkylated naphthalenes, styrene esters, oligomerized alkylphenols, phthalic acid esters, ethylene-vinyl acetate copolymers andcombinations thereof. In one embodiment, the pour point depressant isselected from tetra (long-chain) alkyl silicates,phenyltrstearyloxysilane, and pentaerythritol tetrastearate. In someembodiments, the pour point depressant comprises an ethylene-vinylacetate copolymer, a condensate of chlorinated paraffin and phenol,polyalkyl styrene or the like. The amount of the pour point depressantmay vary from about 0.01 wt. % to about 10 wt. %, from about 0.05 wt. %to about 5 wt. %, or from about 0.1 wt. % to about 3 wt. %, based on thetotal weight of the lubricating oil composition. Some suitable pourpoint depressants have been described in Mortier et al., “Chemistry andTechnology of Lubricants,” 2nd Edition, London, Springer, Chapter 6,pages 187-189 (1996); and Leslie R. Rudnick, “Lubricant Additives:Chemistry and Applications,” New York, Marcel Dekker, Chapter 11, pages329-354 (2003), both of which are incorporated herein by reference.

7. Foam Inhibitors

The lubricating oil composition disclosed herein can optionally comprisea foam inhibitor or an anti-foam that can break up foams in oils. Anyfoam inhibitor or anti-foam known by a person of ordinary skill in theart may be used in the lubricating oil composition. Non-limitingexamples of suitable anti-foams include silicone oils orpolydimethylsiloxanes, fluorosilicones, alkoxylated aliphatic acids,polyethers (e.g., polyethylene glycols), branched polyvinyl ethers,alkyl acrylate polymers, alkyl methacrylate polymers, polyalkoxyaminesand combinations thereof. In some embodiments, the anti-foam comprisesglycerol monostearate, polyglycol palmitate, a trialkylmonothiophosphate, an ester of sulfonated ricinoleic acid,benzoylacetone, methyl salicylate, glycerol monooleate, or glyceroldioleate. The amount of the anti-foam may vary from about 0.01 wt. % toabout 5 wt. %, from about 0.05 wt. % to about 3 wt. %, or from about 0.1wt. % to about 1 wt. %, based on the total weight of the lubricating oilcomposition. Some suitable anti-foams have been described in Mortier etal., “Chemistry and Technology of Lubricants,” 2nd Edition, London,Springer, Chapter 6, pages 190-193 (1996), which is incorporated hereinby reference.

8. Metal Deactivators

In some embodiments, the lubricating oil composition comprises at leasta metal deactivator. Some non-limiting examples of suitable metaldeactivators include disalicylidene propylenediamine, triazolederivatives, thiadiazole derivatives, and mercaptobenzimidazoles.

9. Dispersants

The lubricating oil composition disclosed herein can optionally comprisea dispersant that can prevent sludge, varnish, and other deposits bykeeping particles suspended in a colloidal state. In certainembodiments, dispersants perform these functions via one or more meansselected from: (1) solubilizing polar contaminants in their micelles;(2) stabilizing colloidal dispersions in order to prevent aggregation oftheir particles and their separation out of oil; (3) suspending suchproducts, if they form, in the bulk lubricant; (4) modifying soot tominimize its aggregation and oil thickening; and (5) loweringsurface/interfacial energy of undesirable materials to decrease theirtendency to adhere to surfaces. The undesirable materials are typicallyformed as a result of oxidative degradation of the lubricant, thereaction of chemically reactive species such as carboxylic acids withthe metal surfaces in the engine, or the decomposition of thermallyunstable lubricant additives such as, for example, extreme pressureagents.

In certain aspects, a dispersant molecule comprises three distinctstructural features: (1) a hydrocarbyl group; (2) a polar group; and (3)a connecting group or a link. In certain embodiments, the hydrocarbylgroup is polymeric in nature, and has a molecular weight of at or aboveabout 2000 Daltons, in one embodiment, at or above about 3000 Daltons,in another embodiment, at or above about 5000 Daltons, and in yetanother embodiment, at or above about 8000 Daltons. A variety ofolefins, such as polyisobutylene, polypropylene, polyalphaolefins, andmixtures thereof, can be used to make suitable polymeric dispersants. Incertain embodiments, the polymeric dispersant is apolyisobutylene-derived dispersant. Typically the number averagemolecular weight of polyisobutylene in those dispersants ranges betweenabout 500 and about 3000 Daltons, or, in some embodiments, between about800 to about 2000 Daltons, or in further embodiments, between about 1000to about 2000 Daltons. In certain embodiments, the polar group in thedispersant is nitrogen- or oxygen-derived. Nitrogen-based dispersantsare typically derived from amines. The amines from which thenitrogen-based dispersants are derived are often polyalkylenepolyamines,such as, for example, diethylenetriamine and trethylenetetramine.Amine-derived dispersants are also called nitrogen- oramine-dispersants, while those derived from alcohol are also calledoxygen or ester dispersants. Oxygen-based dispersants are typicallyneutral while the amine-based dispersants are typically basic.

Non-limiting examples of suitable dispersants include alkenylsuccinimides, alkenyl succinimides modified with other organiccompounds, alkenyl succinimides modified by post-treatment with ethylenecarbonate or boric acid, succiamides, succinate esters, succinateester-amides, pentaerythritols, phenate-salicylates and theirpost-treated analogs, alkali metal or mixed alkali metal, alkaline earthmetal borates, dispersions of hydrated alkali metal borates, dispersionsof alkaline-earth metal borates, polyamide ashless dispersants,benzylamines, Mannich type dispersants, phosphorus-containingdispersants, and combinations thereof. The amount of the dispersant mayvary from about 0.01 wt. % to about 10 wt. %, from about 0.05 wt. % toabout 7 wt. %, or from about 0.1 wt. % to about 4 wt. %, based on thetotal weight of the lubricating oil composition. Some suitabledispersants have been described in Mortier et al., “Chemistry andTechnology of Lubricants,” 2nd Edition, London, Springer, Chapter 3,pages 86-90 (1996); and Leslie R. Rudnick, “Lubricant Additives:Chemistry and Applications,” New York, Marcel Dekker, Chapter 5, pages137-170 (2003), both of which are incorporated herein by reference.

10. Anti-Oxidants

Optionally, the lubricating oil composition disclosed herein can furthercomprise an additional antioxidant that can reduce or prevent theoxidation of the base oil. Any antioxidant known by a person of ordinaryskill in the art may be used in the lubricating oil composition.Examples of anti oxidants useful in the compositions include, but arenot limited to, phenol type (phenolic) oxidation inhibitors, such as4,4′ methylene bis(2,6 di tert butylphenol), 4,4′ bis(2,6 ditert-butylphenol), 4,4′ bis(2 methyl 6 tert butylphenol), 2,2′ methylenebis(4-methyl 6 tert butylphenol), 4,4′ butylidene bis(3 methyl 6 tertbutylphenol), 4,4′ isopropylidene bis(2,6 di tert butylphenol), 2,2′methylene bis(4-methyl 6 nonylphenol), 2,2′ isobutylidene bis(4,6dimethylphenol), 2,2′ 5 methylene bis(4 methyl 6 cyclohexylphenol), 2,6di tert butyl 4-methylphenol, 2,6 di tert butyl 4 ethylphenol, 2,4dimethyl 6 tert butyl-phenol, 2,6 di tert 1 dimethylamino p cresol, 2,6di tert 4 (N,N′-dimethylaminomethylphenol), 4,4′ thiobis(2 methyl 6 tertbutylphenol), 2,2′-thiobis(4 methyl 6 tert butylphenol), bis(3 methyl 4hydroxy 5 tert-10 butylbenzyl)sulfide, and bis(3,5 di tert butyl 4hydroxybenzyl). Diphenylamine type oxidation inhibitors include, but arenot limited to, alkylated diphenylamine, phenyl alpha naphthylamine, andalkylated alpha naphthylamine, sulfur-based antioxidants (e.g.,dilauryl-3,3′-thiodipropionate, sulfurized phenolic antioxidants and thelike), phosphorous-based antioxidants (e.g., phosphites and the like),zinc dithiophosphate, oil-soluble copper compounds and combinationsthereof. Other types of oxidation inhibitors include metaldithiocarbamate (e.g., zinc dithiocarbamate), and 15methylenebis(dibutyldithiocarbamate). The amount of the antioxidant mayvary from about 0.01 wt. % to about 10 wt. %, from about 0.05 wt. % toabout 5 wt. %, or from about 0.1 wt. % to about 3 wt. %, based on thetotal weight of the lubricating oil composition. Some suitableantioxidants have been described in Leslie R. Rudnick, “LubricantAdditives: Chemistry and Applications,” New York, Marcel Dekker, Chapter1, pages 1-28 (2003), which is incorporated herein by reference.

11. Multifunctional Additives

Various additives mentioned or not mentioned herein can provide amultiplicity of effects to the lubricant oil composition providedherein. Thus, for example, a single additive may act as a dispersant aswell as an oxidative inhibitor. Multi-functional additives are wellknown in the art. Other suitable multi-functional additives may include,for example, sulfurized oxymolybdenum dithiocarbamate, sulfurizedoxymolybdenum organo pohosphoro dithioate, oxymolybdenum monoglyceride,amine-molybdenum complex compound, and sulfur-containing molybdenymcomplex compounds.

12. Viscosity Index Improvers

In certain embodiments, the lubricating oil composition comprises atleast a viscosity index improver. Some non-limiting examples of suitableviscosity index improvers include polymethacrylate type polymers,ethylene-propylene copolymers, styrene-isoprene copolymers, hydratedstyrene-isoprene copolymers, polyisobutylene, and dispersant typeviscosity index improvers.

Processes of Preparing Lubricating Oil Compositions

The lubricating oil compositions disclosed herein can be prepared by anymethod known to a person of ordinary skill in the art for makinglubricating oils. In some embodiments, the base oil is blended or mixedwith an oil-soluble molybdenum compound; a zinc dialkyldithiophosphateand optionally an additive. In certain embodiments, the oil-solublemolybdenum compound; a zinc dialkyldithiophosphate are premixed followedby addition of the base oil. In other embodiments, the oil-solublemolybdenum compound and zinc dialkyldithiophosphate can be added to thebase oil individually or simultaneously. In some embodiments, theoil-soluble molybdenum compound, zinc dialkyldithiophosphate and theoptional additives are added to the base oil individually in one or moreadditions and the additions may be in any order. In other embodiments,the ester base stocks and the additives are added to the base oilsimultaneously. In some embodiments, the oil-soluble molybdenumcompound, zinc dialkyldithiophosphate and the optional additives arepremixed and the premix is added to the base oil along with a viscosityindex improver.

Any mixing or dispersing equipment known to a person of ordinary skillin the art may be used for blending, mixing or solubilizing theingredients. The blending, mixing or solubilizing may be carried outwith a blender, an agitator, a disperser, a mixer (e.g., planetarymixers and double planetary mixers), a homogenizer (e.g., Gaulinhomogenizers and Rannie homogenizers), a mill (e.g., colloid mill, ballmill and sand mill) or any other mixing or dispersing equipment known inthe art.

Applications of the Lubricating Oil Compositions

In certain embodiments, the lubricating oil compositions provided hereinis suitable for use as motor oils (that is, engine oils or crankcaseoils), in a gasoline or diesel engine.

In one embodiment, the lubricating oil composition provided herein isused to cool hot engine parts, keep the engine free of rust anddeposits, and seal the rings and valves against leakage of combustiongases. The motor oil composition comprises a base oil, oil-solublemolybdenum compound and a zinc dialkyldithiophosphate. Optionally, themotor oil composition may further comprises one or more other additives.In some embodiments, the motor oil composition further comprises a pourpoint depressant, a detergent, a dispersant, an anti-wear, anantioxidant, a friction modifier, a rust inhibitor, or a combinationthereof.

The following examples are presented to exemplify embodiments of thelubricant oil compositions provided herein but are not intended to limitthe subject matter to the specific embodiments set forth. Unlessindicated to the contrary, all parts and percentages are by weight. Allnumerical values are approximate. When numerical ranges are given, itshould be understood that embodiments outside the stated ranges maystill fall within the scope of the claimed subject matter. Specificdetails described in each example should not be construed as necessaryfeatures of the claimed subject matter.

EXAMPLES Example 1

A lubricating oil composition was prepared and used for assessingboundary lubrication properties in the High Frequency Reciprocating Rig(HFRR) test (ASTM D 6079). The composition contained a major amount of abase oil of lubricating viscosity and the following additives, toprovide an SAE 5W-20 finished oil;

(1) 700 ppm in terms of molybdenum content, of a molybdenumdithiocarbamate

(2) 1 wt % of a borated bis-succinimide dispersant

(3) 4 wt % of an ethylene carbonate post-treated bis-succinimide

(4) 164 ppm in terms of calcium content, of a 17 TBN calcium sulfonatedetergent

(5) 2220 ppm in terms of calcium content, of a 148 TBN calciumsalicylate

(6) 1 wt % of an alkylated diphenylamine

(7) 0.2 wt % of hindered phenol

(8) 0.2 wt % of a pour point depressant

(9) 4.8 wt % of a non-dispersant ethylene-propylene copolymerconcentrate

(10) 5 ppm in terms of Silicon content, of a foam inhibitor

(11) The remainder was diluent oil. Diluent oil can be a Gp 1 or Gp 2base oil. However, any diluent oil known to one of skill in the artcould be used.

Example 2

A lubricating oil was prepared in accordance with the formulation ofExample 1 except that 250 ppm in terms of phosphorus content of a zincdialkyldithiophosphate was added. The composition contained 250 ppmphosphorus based on the total weight of the lubricating oil composition.

The zinc dialkyldithiophosphate is synthesized using a mixture of C4 andC6 secondary alcohols. The resulting zinc dialkyldithiophosphate is azinc bis(O,O′-di-(2-butyl/4-methyl-2-pentyl)dithiophosphate.

Example 3

A lubricating oil was prepared in accordance with the formulation ofExample 1 except that 500 ppm in terms of phosphorus content of the zincdialkyldithiophosphate was added. The composition contained 500 ppmphosphorus based on the total weight of the lubricating oil composition.

Example 4

A lubricating oil was prepared in accordance with the formulation ofExample 1 except that 750 ppm in terms of phosphorus content of the zincdialkyldithiophosphate was added. The composition contained 750 ppmphosphorus based on the total weight of the lubricating oil composition.

Example 5

A lubricating oil was prepared in accordance with the formulation ofExample 1 except that 1000 ppm in terms of phosphorus content of thezinc dialkyldithiophosphate was added. The composition contained 1000ppm phosphorus based on the total weight of the lubricating oilcomposition.

Example 6

A lubricating oil was prepared in accordance with the formulation ofExample 1 except that 700 ppm inter ms of molybdenum content of anoxymolybdenum-succinimide complex was used in place of the molybdenumdithiocarbamate.

Example 7

A lubricating oil was prepared in accordance with the formulation ofExample 6 except that 250 ppm in terms of phosphorus content of the zincdialkyldithiophosphate was added. The composition contained 250 ppmphosphorus based on the total weight of the lubricating oil composition.

Example 8

A lubricating oil was prepared in accordance with the formulation ofExample 6 except that 500 ppm in terms of phosphorus content of the zincdialkyldithiophosphate was added. The composition contained 500 ppmphosphorus based on the total weight of the lubricating oil composition.

Example 9

A lubricating oil was prepared in accordance with the formulation ofExample 6 except that 750 ppm in terms of phosphorus content of the zincdialkyldithiophosphate was added. The composition contained 750 ppmphosphorus based on the total weight of the lubricating oil composition.

Example 10

A lubricating oil was prepared in accordance with the formulation ofExample 6 except that 1000 ppm in terms of phosphorus content of thezinc dialkyldithiophosphate was added. The composition contained 1000ppm phosphorus based on the total weight of the lubricating oilcomposition.

Example 11

A lubricating oil was prepared in accordance with the formulation ofExample 1 except that the amount of molybdenum dithiocarbamate wasreduced to 150 ppm in terms of molybdenum content, and 550 ppm in termsof molybdenum content of the oxymolybdenum-succinimide complex wasadded.

Example 12

A lubricating oil was prepared in accordance with the formulation ofExample 11 except that 250 ppm in terms of phosphorus content of thezinc dialkyldithiophosphate was added. The composition contained 250 ppmphosphorus based on the total weight of the lubricating oil composition.

Example 13

A lubricating oil was prepared in accordance with the formulation ofExample 11 except that 500 ppm in terms of phosphorus content of thezinc dialkyldithiophosphate was added. The composition contained 500 ppmphosphorus based on the total weight of the lubricating oil composition.

Example 14

A lubricating oil was prepared in accordance with the formulation ofExample 11 except that 750 ppm in terms of phosphorus content of thezinc dialkyldithiophosphate was added. The composition contained 750 ppmphosphorus based on the total weight of the lubricating oil composition.

Example 15

A lubricating oil was prepared in accordance with the formulation ofExample 10 except that 1000 ppm in terms of phosphorus content of thezinc dialkyldithiophosphate was added. The composition contained 1000ppm phosphorus based on the total weight of the lubricating oilcomposition.

Test Procedure

The High Frequency Reciprocating Rig (HFRR) test (ASTM D 6079) isdesigned to evaluate boundary lubrication properties. In this method, a2 mL sample is placed in the test reservoir of an HFRR and adjusted to astandard temperature. When the sample temperature has stabilized, avibrator arm holding a non-rotating steel ball is lowered until itcontacts a test disk completely submerged in the sample. The ball iscaused to rub against the disk.

The compositions of Examples 1-15 were tested using a 120° C. oilreservoir temperature and were subjected to a 1000 g load. The ball wascaused to rub against the disk with a 1 mm stroke at a frequency of 20Hz for 60 min.

This test was run using samples from Examples 1-15 and the results areshown in Table 2. A graphic description of these results is found inFIG. 1.

TABLE 2 Last 10 Min P⁴ Overall Average content Average Friction ExampleMo Source (ppm) Friction Coefficient Coefficient 1 MoDTC¹ 0 0.10 0.068 2MoDTC¹ 250 0.079 0.053 3 MoDTC¹ 500 0.083 0.069 4 MoDTC¹ 750 0.077 0.0715 MoDTC¹ 1000 0.078 0.076 6 Mo-succ² 0 0.16 0.16 7 Mo-succ² 250 0.0650.050 8 Mo-succ² 500 0.080 0.058 9 Mo-succ² 750 0.080 0.064 10 Mo-succ²1000 0.086 0.073 11 Mixed³ 0 0.17 0.16 12 Mixed³ 250 0.052 0.052 13Mixed³ 500 0.083 0.065 14 Mixed³ 750 0.074 0.060 15 Mixed³ 1000 0.0760.066 ¹Lubricating oil compositions with molybdenum dithiocarbamate hada total molybdenum content of 700 ppm. ²Lubricating oil compositionswith molybdenum-succinimide complex had a total molybdenum content of700 ppm. ³Lubricating oil composition contained a mixture of 150 ppm Moof MoDTC and of 550 ppm Mo of molybdenum-succinimide complex. Thelubricating oil composition had a total molybdenum content of 700 ppm(150 ppm Mo from MoDTC and 550 ppm Mo from Mo-succinimide complex).⁴Phosphorous content in ppm of the zinc dialkyldithiophosphate employedin Examples 1-15.

In addition to measurement of the overall average friction coefficient,the last 10 minute average friction coefficient was determined. Thiscoefficient is useful because it takes approximately 15 minutes from thestart of the test until there is a low friction film on the metalsurface. Both sets of data show friction coefficient minima atphosphorus levels of 250 ppm.

While the lubricant oil compositions provided herein have been describedwith respect to a limited number of embodiments, the specific featuresof one embodiment should not be attributed to other embodiments of thesubject matter claimed herein. No single embodiment is representative ofall aspects of the claimed subject matter. In some embodiments, themethods may include numerous steps not mentioned herein. In otherembodiments, the methods do not include, or are substantially free of,steps not enumerated herein. Variations and modifications from thedescribed embodiments exist. It is noted that the methods for producingthe compositions disclosed herein are described with reference to anumber of steps. These steps can be practiced in any sequence. One ormore steps may be omitted or combined but still achieve substantiallythe same results. The appended claims intend to cover all suchvariations and modifications as falling within the scope of the claims.

All publications and patent applications mentioned in this specificationare herein incorporated by reference to the same extent as if eachindividual publication or patent application was specifically andindividually indicated to be incorporated by reference. Although theforegoing has been described in some detail by way of illustration andexample for purposes of clarity of understanding, it will be readilyapparent to those of ordinary skill in the art in light of the teachingsherein that certain changes and modifications may be made theretowithout departing from the spirit or scope of the appended claims.

1. A lubricating oil composition comprising: i) a major amount of a baseoil, ii) at least one oil-soluble molybdenum compound and iii) a zincdialkyldithiophosphate compound, wherein the molybdenum content derivedfrom the molybdenum compound is at least 10 ppm Molybdenum based on thetotal weight of the lubricating oil composition and the phosphoruscontent derived from the zinc dialkyldithiophosphate compound is about200 ppm to 500 ppm based on the total weight of the lubricating oilcomposition.
 2. The lubricating oil composition of claim 1, wherein theoil-soluble molybdenum compound is selected from molybdenumdithiocarbamate, molybdenum dithiophosphate, molybdenumdithiophosphinate, molybdenum xanthate, molybdenum thioxanthate,molybdenum sulfide and a mixture thereof.
 3. The lubricating oilcomposition of claim 1, wherein the oil-soluble molybdenum compound isselected from molybdenum dithiocarbamate, molybdenum-succinimide complexand a mixture thereof.
 4. The lubricating oil composition of claim 1,wherein the molybdenum content derived from the molybdenum compound isfrom about 10 to 10,000 ppm molybdenum based on the total weight of thelubricating oil composition.
 5. The lubricating oil composition of claim1, wherein the molybdenum content derived from the molybdenum compoundis from about 50 to 1500 ppm molybdenum based on the total weight of thelubricating oil composition.
 6. The lubricating oil composition of claim1, wherein the molybdenum content derived from the molybdenum compoundis from about 250 to 1200 ppm molybdenum based on the total weight ofthe lubricating oil composition
 7. The lubricating oil composition ofclaim 1, wherein the zinc dialkyldithiophosphate comprises a straight orbranched alkyl group having 3 to 30 carbon atoms.
 8. The lubricating oilcomposition of claim 1, wherein the zinc dialkyldithiophosphatecomprises an alkyl selected from ethyl, propyl, butyl, pentyl,methylpentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl,tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, and octadecyl.9. The lubricating oil composition of claim 1, wherein the phosphoruscontent derived from the zinc dialkyldithiophosphate compound is about200, 250, 300, 350, 400, 450 or 500 ppm based on the total weight of thelubricating oil composition.
 10. The lubricating oil composition ofclaim 1, wherein the phosphorus content derived from the zincdialkyldithiophosphate compound is about 250 ppm based on the totalweight of the lubricating oil composition.
 11. The lubricating oilcomposition of claim 1 further comprising at least one additive selectedfrom the group consisting of antioxidants, antiwear agents, detergents,rust inhibitors, demulsifiers, friction modifiers, multi-functionaladditives, viscosity index improvers, pour point depressants, foaminhibitors, metal deactivators, dispersants, corrosion inhibitors,lubricity improvers and combinations thereof.
 12. A method of making alubricating oil composition comprising the step of mixing: i) a majoramount of a base oil, ii) at least one oil-soluble molybdenum compoundand iii) a zinc dialkyldithiophosphate compound, wherein the molybdenumcontent derived from the molybdenum compound is at least 10 ppm based onthe total weight of the lubricating oil composition and the phosphoruscontent derived from the zinc dialkyldithiophosphate compound is about200 to 500 ppm based on the total weight of the lubricating oilcomposition.
 13. A method of lubricating a motor engine comprising thestep of operating the engine with the lubricating oil composition ofclaim
 1. 14. The method of claim 15, wherein the molybdenum contentderived from the molybdenum compound is from 10 to 10,000 ppm based onthe total weight of the lubricating oil composition.
 15. The method ofclaim 15, wherein the phosphorus content derived from the zincdialkyldithiophosphate compound is about 200, 250, 300, 350, 400, 450 or500 ppm based on the total weight of the lubricating oil composition.16. The method of claim 15, wherein the phosphorus content derived fromthe zinc dialkyldithiophosphate compound is about 250 ppm based on thetotal weight of the lubricating oil composition.